[[File:The_White_Man's_Burden"_Judge_1899.png|thumb|right|Figure 1: "The White Man's Burden" (1899) depicts Caucasian men carrying a burden of 'uncivilised' Filipino and Puerto Rican men to civilisation.}}

Between 1939 and 1945, the Nazi regime led by Adolf Hitler exterminated over 6 million Jews in the worst genocide in human history. The Holocaust resulted in two-thirds of Europe's Jewish population being wiped out, as well as the deaths of many people who were homosexual, black or disabled, and this is only a small fragment of a war which led to the deaths of 60 million people (Musolff, 2007). Today, we look back on this extreme result of prejudice as a cultural warning to treat one another with kindness. But several questions remain unanswered - how could things get to this extreme stage? Why do people show hatred towards those who are different? How was so much of Germany indoctrinated into this racial cleansing? All of these questions fall into the psychological field of intergroup prejudice. This chapter evaluates research on intergroup prejudice to provide some answers to these questions, focusing on the emotional experience of disgust.

Disgust is our "oldest emotion", and protects us from harmful threats such as poison by causing withdrawal (Reeve, 2015). From infancy, we instinctively and automatically show disgust towards foods which are bitter in order to protect ourselves from contamination and death (Zhong et al, 2010). However, disgust has also been found to have a social component, and has been implicated in prejudice. Just like the sight of spoiled food or the smell of vomit, a biological disgust reaction can be exhibited in response to people. This chapter will investigate the biology of disgust, the ways it is expressed in social prejudice such as racism, how social disgust develops, case studies of disgust being implicated in extreme prejudice events such as the Holocaust, and how prejudice can be overcome with the knowledge that emotions are at play.

The insula is a fold that lies between the frontal and temporal lobes, above the subcortical brain. It is comprised of two halves; the posterior insula, which has been found to monitor states such as heart rate, fatigue, pain and cravings, and the anterior insula, which evaluates these states and directs them towards consciousness (Reeve, 2015). As a result, the insula serves two unique functions - creating gut feelings in the subcortical brain, and relaying these impulses for evaluation in the cortical brain.

A fMRI neuroimaging study by Wicker et al (2003) found that disgust and pleasure responses were both expressed in the anterior insula, but disgust was experienced bilaterally while pleasure was confined mostly to the right hemisphere of the brain. A second fMRI study by Shapira et al (2003) also found most notable activation in the insula upon the viewing of a disgust-inducing image. Furthermore, the insula has been found to respond to images showing contamination and mutilation, but not to images showing attacks (Wright et al, 2004).

Figure 3: Acne can elicit disgusted responses, but it is not an indicator of contagion.

The centre of study into disgust-related prejudice is the behavioural immune system (BIS). In contrast to the body's physical immune system, the BIS protects an organism by preventing it from coming into contact with contamination that could lead to death or disease in the first place. In this way, the BIS acts as a "first defense" against disease. This is why humans frequently exhibit disgust when confronted with potentially infectious agents such as blood, faeces and vomit (de Zavala et al, 2014).

Studies have found, however, two factors that lead the BIS to assist prejudice:

The BIS responds not only to physical cues of disease, but to indicators of moral contamination (Terrizzi et al, 2010); and

For example, a study by Schaller & Park (2011) found that a perceived threat of infection predicts a prejudicial response against the disabled, the obese and the elderly, despite none of these attributes being inherently contagious. In addition, sensory cues such as acne and body odour are not perfectly correlated with infection yet elicit disgust anyway (Schaller & Park, 2011). People with strong sensitivity to disgust have also been found to exhibit more moral prejudice - a study of Christian students by Choma et al (2016) found that disgust sensitivity was a better predictor of prejudice towards Muslims than was their religious affiliation.

The reason for the BIS's overactivity appears to be safety. To an organism, there is little consequence to being too safe, but the consequences of failing to detect a pathogen are as severe as illness and death (Schaller & Park, 2011). In moral terms, BIS activity serves to protect a social group from contamination from outsiders, preserving way of life and preventing conflict (Matthews & Levin, 2012).

Two ideological orientations have been found to predict intergroup prejudice; social dominance orientation (SDO) and right-wing authoritarianism (RWA) (Duckitt, 2001). These orientations have been described by intergroup prejudice researchers as the two key belief factors in the experience of non-biological prejudice, and the amount of each factor that each individual has contributes to how prejudiced they are, and to whom they exhibit the most prejudice (Hodson & Costello, 2007).

Those high in SDO view the world as competitive, accept inequality, and endorse social hierarchies (Duckitt, 2001). Prejudicial disgust assists those high in SDO as it encourages social distinctiveness and the maintenance of hierarchies. Meanwhile, those high in RWA strictly follow norms and traditions, respect and submit to authority, and are aggressive towards those who don't. RWA ideology is focused on controlling a chaotic world through the implementation of strict order, and as a result, those high in RWA often exhibit prejudice towards "deviants" such as homosexuals, criminals and those who view pornography (Hodson & Costello, 2007). Both SDO and RWA are types of conservatism.

Interestingly, RWA is more associated with disgust than SDO. In an experiment, Matthews and Levin (2012) measured the types of emotions associated with economic threats (SDO) and value threats (RWA) and found that while economic threats (such as taking resources) were correlated with fear and anger, value threats (such as sexual promiscuity) were correlated with disgust.

The dual-process model is an important social theory because it adds a social-nurture dimension to established research on disgust responses. By looking at two different value systems which influence prejudice, we can start to infer why the BIS might be active when a non-biologically contaminative factor is present. Two key questions arise: do individual variations in the BIS create people high in RWA and SDO? Or, do people develop RWA and SDO tendencies which then influence the way their BIS works? These questions will be discussed in the following section.

Quiz yourself

The behavioural immune system (BIS) is:

Made up mainly of white blood cells which destroy disease.

The body's way of preventing us from coming into contact with contamination.

A concept introduced by psychoanalytic psychologists.

Strengthened by diet and exercise.

Which of these individuals is likely to be high in right-wing authoritarianism (RWA)?

A woman, 28, who works from home, has no children, and wants to study business.

A man, 35, who runs a successful corporation, is very success-focused, and demands to be rewarded for his accomplishments.

A woman, 19, who goes out drinking every Friday night and often skips school.

A man, 62, who goes to Church every Sunday, supports his president, and frequently writes anti-gay marriage editorials.

When a person has cues within their physical appearance that indicate unwellness - for example, the disabled, the obese and the elderly - prejudiced responses can partially be explained by the behavioural immune system inaccurately and automatically detecting physical contamination that isn't there. But why has the BIS evolved to incorporate social contamination? When someone has no signs of physical illness or deformity, and is simply of a different race, religion or lifestyle, why do we sometimes elicit disgust? This section will discuss the possible factors behind the development of a social component to disgust.

An evolutionary perspective to disgust stipulates that it has evolved to serve three distinct purposes: pathogen avoidance, mate choice, and social interaction (Tybur & Lieberman, 2009). As pathogen avoidance has been discussed above, this section will cover mate choice and social interaction.

Figure 4: A couple getting married. Disgust is especially prevalent in mate choice in order to prevent choosing an inferior partner.

Sexual disgust has been found to be particularly strong. When told to imagine having sexual intercourse with an obese person, participants in an experiment by Lieberman et al (2012) expressed much greater disgust than when confronted with pathogen-related or moral stimuli. A study of saliva by O'Handley et al (2017) found nearly indistinguishable levels of alpha-amylase, an enzyme indicative of stress, in the mouths of men who were exposed to images of men kissing and images of traditionally disgusting stimuli such as maggots. Similarly, an experiment by de Zavala et al (2014) found that people who imagined using the phone of a homosexual man rather than a heterosexual man expressed significantly higher desire to use a cleansing wipe afterwards. There is a possibility that this disgust serves an evolutionary purpose, making sure that potential mates who are sexually unsuitable due to health or behaviour are not chosen. This biological-evolutionary perspective is supported by experiments which have found prejudiced reactions are expressed even in people who have rated themselves as low-prejudice (Monteith, 1993).

Disgust is thought to have a social interactivity role in preventing contamination of group values that would lead to conflict (Taylor, 2007). This is reflective of the evolutionary perspective's view of emotions as adaptive mechanisms that help to navigate threats and problems (Reeve, 2015). Historically, this has been thought to protect clan resources such as food and prevent contamination by disease (Taylor, 2007). More presently, those who have a strict sense of personal identity and morals (high RWA) or a set way of thinking about competition and hierarchy (high SDO) display this when exhibiting disgust- or anger-based emotions towards those who threaten to change these circumstances, protecting the status quo. Furthermore, there may also gender differences in socialisation-based prejudice, such that men are often found to express more disgust especially in sexual situations while women tend to express fear-based prejudice to prevent attacks (Parrott, 2009). Finally, an interesting perspective on racism is that there is a possibility that the human brain has simply not evolved to be welcoming to other races yet, as cross-racial interaction has only happened extremely recently in human history (Parrott, 2009). Thus, some prejudices may be a "growing pain" of social integration and globalisation.

Figure 5: Children often learn from social modelling. This might be from parents, or from cultural influences such as television.

Former South African president and anti-apartheid activist Nelson Mandela said, "No one is born hating another person because of the color of his skin or his background or his religion." (Mandela, 2013). If this is true, then social components to prejudice must be learnt.

Psychologist Albert Bandura proposed the social learning theory (later social-cognitive theory) which stipulates that people can learn in two ways: through personal experience, and by observing and modelling the behaviour of others (Bandura, 1971). An experience with a rude Indian man may lead someone to assign similar hypotheses towards Indian people, creating a personal experience-based prejudice that leads to disgust upon encounters, especially if reinforced by another, similar experience. Conversely, prejudice may be learnt through modelling of already-prejudiced people. As learning by experience is often dangerous, Bandura argues that learning through observation and replication provides a way for people to learn without having to put themselves in danger (Bandura, 1971). Socialisation has been found to be a key factor in the development of ideology (Duckitt, 2001), and as a result, many researchers believe that disgust responses to outgroups, while partially biological, have a learned component (Hodson & Costello, 2007). A study by Barr & Neville (2008), for example, found black students internalised their parents' attitudes towards racism and that this predicted their own attitudes and behaviours.

Case study: Nazi Germany

Figure 6: A group of young men in the Hitler Youth, or Hitlerjugend (circa 1933). Indoctrination of youth was part of a wider strategy to further the Nazi Party's aims.

From the atrocities of the Holocaust comes a pertinent question: how were Adolf Hitler and the Nazi Party able to gain compliance and even favour from the German population to such an extent? The answer lies, in part, due to the use of disgust-based imagery, and the role of disgust in dehumanising a target.

In his autobiography Mein Kampf, Hitler uses disease- and pest-based imagery to describe the Jews. Germany was presented as a human body, with the Jews a disease that needed to be eradicated (Musolff, 2007). It is argued that this personification of Germany and dehumanisation of Jews is what made it possible for genocide to be committed. Researcher Robert Sternberg (2003) proposed a triarchic model of hate, arguing that pure hate can only exist with a combination of anger, fear and disgust working together. Anger and fear create passion, contempt fosters commitment, and disgust negates intimacy. With these three attributes, hate crimes can be carried out effectively, powerfully, and without remorse. By dehumanising an outgroup, perpetrators of violent crimes negate guilt. After all, they are in the right if they are eradicating something threatening and subhuman (Taylor, 2007).

The indoctrination of the German people may also involve other elements of intergroup disgust study, such as:

The BIS - if the German people were taught to see Jews and other minorities as a threat to resources or health, a disgust response was a logical next step to withdraw from the threat.

Evolutionary perspective - ideas about the re-emergence of Germany as a great nation were conveyed, leading to a "survival of the fittest" mentality. The German people had to be superior, and disgust was shown towards Jews, who were perceived as inferior. This protects the social hierarchy, indicating high SDO.

Social learning theory - the German people may have learned from each other through imitation and observation, leading to an exponential increase in the spread of Nazi ideology. In later stages, Mein Kampf was compulsory reading, young Germans had to join the Hitler Youth, and entire school curricula were dedicated to indoctrination, leading to a deep and inescapable set of social guidelines from which to learn. (Voigtländer & Voth, 2015).

However, it is important to remember that disgust is only one element in the experience of prejudice. Other factors in the indoctrination of the German people are likely to include fear due to the potential for imprisonment or murder if dissent was shown, and anger at the economic conditions they had inflicted upon them following the end of World War I. While disgust frequently plays a key role in prejudice, it is only one of several factors.

Figure 7: Rallies in San Francisco, July 2016, following the shooting deaths of unarmed black men Alton Sterling and Philando Castile.

To conclude the chapter, we look at strategies to overcome prejudice. This will help you to understand why prejudice is negative within the context of society, and how psychological interventions can be applied to reduce it.

For an attitude to be considered prejudice, it must be both unrealistic and unfair. For example, prejudice against overweight people is typically unfair because fat is not contagious, obesity is not a direct threat to others, and gut responses are typically not based on reality but on a false-positive signal from the BIS or a violation of personal control attitudes found in those with high RWA.

It is important to overcome prejudice because it can lead to several consequences such as employment discrimination and violence. Obese people have been found to suffer employment discrimination frequently, and be perceived to have a lower social status due to their weight (Vartanian et al, 2013). Homosexual men are commonly victims of hate-fuelled violence, such that "gay panic" has even been a historical legal defense in murder cases (O'Handley et al, 2017). Similarly, a neuroimaging study by Capestany and Harris (2014) looked at emotion-related areas of the brain during legal deliberation and inferred that activation of these areas may bias decisions. This is dangerous as it may lead to bias in judicial and law enforcement systems, as is currently being debated in the wake of several shootings of unarmed black men by police in the United States. It is currently estimated that American judges hold a moderate to large degree of racial bias (Capestany & Harris, 2014).

Researchers have found that intergroup contact reduces prejudice in most cases. Reasons for this include providing better knowledge of the outgroup, reducing anxiety, and increasing empathy. Further, studies have found that this effect is more significant for members of majority groups, potentially indicating that contact with a minority outgroup may alleviate anxiety about unfamiliar people, values and situations, and dispel inaccurate stereotypes (Pettigrew & Tropp, 2008).

However, other methods for reducing prejudice have had mixed results. In a meta-analysis by Paluck & Green (2009), it was found that trying to suppress stereotypes had the opposite effect, making the stereotype more persistent. Empathy-centred activities such as writing essays from the perspective of an elderly person created higher ratings on the outgroup, but did not affect personal beliefs or opinions on government policy. Promotion of critical thinking to avoid faulty generalisations had moderate success.

There is most evidence for interventions that increase factual knowledge of outgroups, increase accountability of ingroups, increase empathy, and are applied over time (Paluck & Green, 2009; Monroe & Martinez-Marti, 2008). Thus, a successful intervention will be multidimensional. Interventions are also most likely to work on people who rate themselves low in prejudice, as prejudiced responses in these people are found to already create cognitive dissonance and lead to self-regulation before any external moderation is applied (Monteith, 1993).

If you would like to reduce your prejudice, it may help to ask yourself the following questions:

Is there evidence that these people pose a realistic and tangible threat to me?

Do I have enough knowledge about these people and their way of life?

Am I relying on stereotypes that are not necessarily accurate?

Is an already-present feeling affecting my judgment? Would I usually make this choice?

What consequences might I face for my current opinions and behaviour? (e.g. losing friends)

How would I feel if someone acted like this towards me?

Following this, you might be able to gain a better understanding of your prejudice and where it comes from, and work to make changes by finding information, using more advanced insight, and experimenting with different interactions with those who make you feel this way.

A tool commonly used to measure prejudice is the Implicit Association Test (IAT), which has been used in several of the studies referenced in this chapter. If you would like to try the IAT for yourself, it can be found here.